Amygdala: Yes, I love you and I remember you.

We are living creatures. Humans, animals…We have to survive in life. We communicate through people, as we do not live alone but in a society. For that, we use two aspects. Cognition and emotions. So here are the key words before we start “amygdala”.

Amygdala means “almond” in Latin. See the two pictures below. The one on your right is an MRI image of amygdala on a coronal view (the way you would cut a bread; sorry for the analogy; I am so anatomist). Amygdala resembles an almond, doesn’t it? The Ancient scientists were creative.

Where is amygdala?

The human skull is composed of different bones. One bone just over your ears, put your finger over your ear, here is your temporal bone. The lobes of the brain also lie in these bones with the same names. So your temporal lobe is under your finger now. Why did they name it “temporal”? Well, it comes from the term “time”. The connection is one starts to have grey hair starting from there as time goes by.

Here is a picture of Ben Stiller, one of my favorite actors, as I like romantic comedies. And here is more information for you. Open the temporal lobe and look inside, the medial temporal lobe (medial means close to the middle of something in the body, not close to the outside) as we anatomists call it. You will see 3 brain structures there. In the middle hippocampus, above it amygdala, under the hippocampus parahippocampus. And when someone says medial temporal lobe, basically you remember these structures and you remember that they are about remembering; e.g. memory. So the temporal lobe; grey hair; comes from “time” and medial part is about memory. Interesting, no? When it was named, it was not known that it was about memory.

A person is walking at the street approaching you. You just don’t like him and do not want to talk to him. Let’s say he is a politician, not your favorite. You are in the Middle East and getting ready to take off one of your shoes to throw at him. So here are the basic questions about your brain? How did you recognize him? Who is he? Amygdala is not in the scene yet. It is your hippocampus (next post) that gives you the facts. A list of information about him. Your reaction is a result of your emotional history; why are you reacting this way? Not because you remember his name, etc. But you should remember all these before you react. Amygdala is now in the scene with its role in “emotional processing”, “emotional learning” and “emotional memory”.

Let me take you again to the same street. Now it is after midnight; and not a safe place of the city to hang out after midnight. But you are there somehow. A “Oh-my God” looking not so well dressed guy stops you in the middle of the street where you are alone and asks for some change. You say “Sorry, I do not have any”, then the next thing you realize is a shining knife in dark. What do you do? You escape with all the blood in your legs, or you have a fight for your life. So what do you need? Fear. You should have the crisis plan. Hippocampus again tells you “this is a knife and can hurt or kill you”. Amygdala says “and you should freak out,now!”. Stress (too much is harmful though) is the key for survival for that night. Thanks God you have an intact amygdala for some emotional processing.

The amygdala as a key brain structure for acquisition and storage of fear memory traces. Emotionally significant experiences tend to be well remembered, and the amygdala has a pivotal role in this process. If you have an ordinary dinner with an ordinary friend, or have a dinner where you propose to your future wife, it is more likely that you remember the one with the ring in your pocket. Let me say that it is also important for your survival (so that the wife does not nag you when she asks you what she was wearing that night).

Functional neuroimaging studies have provided strong support for a critical role of the amygdala in emotional processing. Research on the neural systems underlying emotion in animal models over the past two decades has implicated the amygdala in fear and other emotional processes. Behavioral data suggest that fear stimuli automatically activate fear and capture attention. This effect is likely to be mediated by a subcortical brain network centered on the amygdala.

Smelling

Amygdala and the other structures of the medial temporal lobe where it is located is a member of the limbic system. The system was there in the brains of the first mammals. So amygdala is a part of the oldest region/system of the brain. What does it tell us? Something common with animals. Reproduction, sexual behavior, aggression, response to stress (fight or flight), emotions, survival. Amydala is important in smelling in our animal friends. Sexual arousal and survival (you smell the danger). This role and part of amygdala is not a big deal in humans, though.

This is good. But you can be in trouble on a plane when amygdala and the limbic system dominates in your brain if you are afraid of flying; sending “there is danger, panic, panic!” messages when there is none. Panic attacks? Yes, we have amygdala in the scene.

Psychologically induced stress with the blood pressure-regulatory system

Structural MRI studies where we have the volume of amygdala in several diseases (such as in major depression) have inconsistent results. There might be different reasons for that, but one reason might be amgydala is composed of different nuclei groups, oranges and apples together, these nuclei (plural of nucleus) function differently. Functional neuroimaging studies (functional MRI being again the most popular), animal studies are very useful as well.